Aminoazobenzene, acetylation

A striking feature of disperse dye development in recent decades has been the steady growth in bathochromic azo blue dyes to replace the tinctorially weaker and more costly anthraquinone blues. One approach is represented by heavily nuclei-substituted derivatives of N,N-disubstituted 4-aminoazobenzenes, in which electron donor groups (e.g. 2-acylamino-5-alkoxy) are introduced into the aniline coupler residue and acceptor groups (acetyl, cyano or nitro) into the 2,4,6-positions of the diazo component. A PPP-MO study of the mobility of substituent configurations in such systems demonstrated that coplanarity of the two aryl rings could only be maintained if at least one of the 2,6-substituents was cyano. Thus much commercial research effort was directed towards these more bathochromic o-cyano-substituted dyes. 

SYNS -ACETYL-N -METHYL-4 -AiMINO-N,N-DIMETHYL-4-AMINOAZOBENZENE 4-(N-ACETYL-N-METHYL)AMINO-4 -(N, N -DIMETHYL. MINO)-AZO-BENZENE N, N -DIMETHYL-4 -AMINO-N-ACETYL-N-MONOMETHYL-4-AMINOAZOBEKZENE N-(4-((4-(DIMETHYL. MINO)PHENYL)AZO)PHENYL)-N-METHYLACETAMIDE... 

Many substituted azobenzenes belong to the azobenzene type, as well. Substitution may shift the n —> it band from 440 nm (azobenzene), to 465 nm (hexamethylazobenzene), to 480 nm (2,2 -dimethyl-4,6,4 ,6 -tetra-tert.butylazobenzene), and even to 520 nm (hexaphenylazobenzene). Hydrocarbon, halogen, nitro, carboxy, acetyl, hydroxy, m-amino" and even 2,2 4,4 ,6,6 hexaphenyl substitution— influences the (7i,7t )-(n,7i ) state energy gap, but not so much as to shift the molecule into the aminoazobenzene group. In the context of this book, it is important that the long-chain and polymeric molecules containing azobenzene units coupled by means of hydroxy and carboxy substituents are of the azobenzene type. 

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